1. Field of the Invention
This invention concerns an alignment tool for interconnecting cooperatively threaded members in axially aligned engagement. More particularly, this invention concerns an alignment tool for threadably interconnecting a drill collar and a stabilizer in axial alignment without damaging the threads of either.
2. General Discussion of the Background
The bottom hole assembly of a rotary oil well is usually comprised of a drill bit suspended at the bottom of a plurality of drill collars. The drill collars are often 30 foot long pipes having, for example, an 8 inch outer diameter in a 121/4 inch diameter hole. The drill collars are extremely heavy, and provide the downward force which must be applied to the drill bit in order for drilling to occur properly. The drill collars are joined in threaded, end to end engagement. Stabilizers are often located between sections of the drill collar, and these stabilizers help space the drill collar from the surrounding walls of the hole or casing.
In conventional applications, 10 to 15 heavy drill collars are used above the drill bit. A drill string typically having about a 41/2 inch outer diameter in a 121/4 inch diameter hole, is connected above the collar, the drill string communicating with the rotary mechanisms at the surface so that rotation of the drill string will rotate the collars and drill bit for drilling to occur.
Each section of drill collar is a heavy tubular member having an internally threaded "box end" and an externally threaded, reduced diameter "pin end". A stabilizer section is also a heavy tubular member having an internally threaded "box end" and an externally threaded, reduced diameter "pin end". Each stabilizer is provided with elongated blades which project radially outwardly from the stabilizer to enlarge the stabilizer's outer diameter to approximately the diameter of the hole being drilled.
In order to assemble the stabilizer and drill collar, it is necessary to connect a pin end of a drill collar section to a box end of a stabilizer section. This is an exceedlingly difficult chore since the stabilizers and drill collars have been made very heavy (200-300 pounds per foot) in order to provide the downward force required by the rotary drill bit. The heavy weight of these members makes it difficult to threadably engage them since their weight causes binding between their threads.
Several prior mechanisms have been proposed for axially aligning tubular members such as pipes. For example, U.S. Pat. Nos. 4,432,648 and 4,492,134 disclosed pipe alignment tools in which hydraulic rams hold adjacent pipe ends in spaced engagement during alignment, then permit controlled movement of the ends towards each other so that rotational engagement may be achieved without binding. These tools suffer from the drawback, however, of requiring sources of hydraulic pressure for operation, and are also unsuitable for the very heavy weight of the drill collar and stabilizing members.
U.S. Pat. No. 4,403,666 discloses a transfer arm which clamps tubular members with a clamp. The clamp is permitted to move under the force of axial loads applied under tubular handling operations, which movement reduces wear and damage to the threaded end of a clamped down hole tubular. Such an apparatus is once again unsuitable for interconnecting the very heavy drill collar and stabilizer.
U.S. Pat. No. 1,481,652 describes a pipe rotating attachment which rotates drill pipe for the purpose of making and breaking drill pipe joints. Rotation is achieved by attaching a clamp to a lower pipe portion, then interconnecting the clamp to a rotary table with a stake. Rotation of the table turns the lower pipe section to engage and disengage threads. Such a device fails to appreciate or overcome the damage caused when heavy, cooperatively threaded members bind each other's threads.
It is accordingly an object of this invention to provide a tool for aligning and interconnecting first and second cooperatively threaded members, such as a drill collar and a stabilizer, without binding or damaging the threads of the members.
It is yet another object of the invention to provide such a tool which will reliably function even when the cooperatively threaded members are very heavy.
Yet another object of the invention is to provide such a tool that will hold the very heavy members in a vertically upright position without permitting them to topple.
Finally, it is an object of this invention to provide such a tool that allows both axial alignment without binding and manual rotation of one of the members in a single tool.